Aik-cirgulatibtg stovepiee



R. ELLSDORF AIR CIRCULATING STOVEPIPH Filed Dec March 24, 1931.

Patented Mar. 24 1931 ROBERT nLLsnoRn, or CHICAGO, ILLINOIS AIR-GIRGULATING srovnriirn Application filed December 30, 1929. Serial No. 417,434.

Myinvention relates to means for utilizing a part of the heat of the combustion gases whlch pass up the stove pipe froma stove, and particularly from a coal-burning heater' or other stove, by using'the heat of the gases within'the-stove pipe for warming air.

For this purpose, it has heretofore been customary to interpose a drum bet-ween the stove and the usual stove pipe, or between twosections of the stove pipe, the drum being constructed so that air can circulate through it.

In practice, suchdrums are usually quite short in proportion to the length of the stove pipe, this being necessary both because of the difficulties in constructing such drums in long lengths and because of the prohibitive costs of drums of considerable length. Consequently, such drums usually receive heat from only asmall fraction of the total length of stove pipebetween the stove and the chimney, thereby still wasting the greater part of the heat of the combustion gases which pass through the stove pipe.

Furthermore, such air-heating drums are usually both clumsy and unsightly, and do not readily lend themselves to'the important purpose of heating air for warming rooms in a story of the house above the one in which the stove is located. So also, such drums cannot readily be constructed so that each drum will include both the usual upright portion of the stove pipe and the horizontal pipe portion which inrmany cases extends near the ceiling of the room for a' much greater lengltl'i than the upright portion. Unless heat within these horizontal stove pipe stretches is also'included, the user attains only a small part of the possible efi'ectiveness which such drums could have even if tall up- 4 right drum construction were employed.

It has also heretofore been proposed to employ air pipes extending through stretches'of stove pipes, but this has not proven practical because of the difficulties of securing proper joints in both pipes when one is'housed by the other, the difficulties of allowing for va-' riations in needed lengths of the two pipes, and the additional ditliculty of keeping the two pipes suitably spaced to avoid both rattling and the deposit of soot between them.

' in which My present invention aims to overcome all of the above recited objections in a simple and inexpensive manner, and to provide acomhined stove pipe and air pipe which can readily be manufactured in sections arranged so that the needed'sections can readily be interposed between a stove and a chimney'regardless of the intervening'distance or of the number of elbows required in the piping; and which will permit the air pipe to extend for almost the entire length of the stove pipeso as to utilize nearly all of the heat which passes up the chimney from an ordinary stove pipe. Furthermore, my invention aims to provide such sectional twin pipes in aform in which they will be equally suitable in connection with hot air furnaces for prewarming part of the air supplied to the furnaces.

More particularly, my invention aims to provide such a combination stove pipe and air pipe in the form of twin-pipe sections in which each section of the air pipe extends within the corresponding section of the stove pipe and is rigidly secured to the latter so that the air pipe is freely'spaced for almost its entire length from the bore of the stove pipe. V 7

so also, my invention aims to provide such combination stove pipe and air pipe sections, which I am hereafter designating as aircirculating stove pipe sections 'as units, designed so that they can readily be telescopically coupled 'to one another or to the stove and the chimney with the" same ease as if they were ordinary stove pipes, and regardless of whether such pipe sections are of straight or elbow formation.-

, Still further and also m-ore'detailed objects will appear from the following specification and from the accompanying drawings,

Fig. 1 is a view showing a heating stove connected by the aircirculating stove pipe of my invention to ,a chimney, withboth the stove pipe'and the air-pipe portions in central and'longitudinal section, and with the air-pipe arranged for supplyingwar mair to an upper room. g

Fig. 2 isfa fragmentary and enlarged longitudinal section through an upright portlon of the air-circulating stove pipe, the section being taken along the common diametric plane of both the stove piping and the airpipe, showing both end portions of one unit section and an attached portion of another unit section of my air-circulating stove pipe. Fig. 3 is atransverse section taken along the line 33 of Fig, 2. V

Fig. 4 is a similar section showing a modified form of pipe spacing boss.

Fig. 5 is aperspective view of the upper portion of a unit section of my air-circulating of my sectional units a stove pipe of standard form and standard length, although this is preferably of a somewhat larger bore than the size generally used with thesame stove, so as to allowinterior space for the air piping without diminishing the effective cross-sectional area of the stove aipe.

.Theouter or stove pipe portion of each section extends in generally cylindrical formation from its lower end to within a short distance (as for example two inches) of its upper end and has theportion above this point contract-ed to an exterior diameter corresponding substantiallyto the bore of the main'portion of the pipe. This is commonly done by forming the short upper pipe end 1 ith longitudinal corrugations of relatively small width, and a projecting bead 2 may be formed on the pipe at the juncture of this contracted pipeend with the main stove-pipe portion 3.

This main stove pipe portion is provided at a plurality of points spaced longitudinally of the pipe with counterpartindentations or inwardly directed bosses l, desirably of considerably greater depth radially of the pipe than the thickness of the pipe, these indentations having their axes in a common plane 5 diametric of the said stove pipe portion;

Bearing against the'inner ends of the in dentations and extending lon itudinally of the stove pipe is an air pipe section 6 of considerably smaller diameter than the bore of the stove-pipe, this air pipe section having its axis in the said diametric plane 5 and being "igidly secured '(as by welding) to each of the indentations. i

The air pipe section desirably has its lower end flush with the lower end of the stove pipe portion to which it is secured (as shown in the lower part of Fig.2), but has its upper a fragmentary section. similar to r end projecting for some distance beyond the I it for a length corresponding to that of the said contracted stove pipe portion 1 into tight fitting relation to the upper end of the aforesaid air pipe portion.

Viith each twin-pipe section of my aircirculating stove pipe thus arranged, the air pipe in each section projects beyond the upper end of the stove pipe, as shown in Fig.

This makes it easy for the user to couple any two such sections to each other by first slipping the lower end ofthe air pipe of one section over the projecting end of the air pipe of the second section, then relatively rotating the two sections until their stove pipes are in alinenient, and thereafter forcing the two sections toward each other until the end of the stove pipe of one section abuts against the head 2 on the other section.

By making the contracted upper portion 621.025 the air pipe section longer than the upper contracted part 1 of the stove pipe section and making the exterior diameter of the said air pipe portion 6A of such size as to fit the bore of the main portion 6 of the air pipe, I thus secure a tight and rigid, interfitting of both pipes in the coupled sections while also facilitating the assembling.

Toprovide for bends in the piping, I provide correspondingly constructed elbows comprising stove-pipe elbows 8 each having an air-pipe elbow 9 supported in it in the same eccentric relation in which the air pipe is supported in the stove pipe of a straight section or unit of my air-circulating stove pipe.

For attaching to a stove 1 1, I desirably provide a stove-fitting section 10 within which an air-pipe section 11 is mounted in similar eccentric disposition, this air-pipe section being of an elbow form to present an inlet portion 11B extending through one side of the stove-pipe section 10, so that a depending inlet duct 12 can be supported from the outer end of the inlet portion 11B. If necessary, such stove fitting sections of my air-circulating stove pipe can easily be made by any tinsmith provided with one of my regular straight section units.

F or irregular heights or lengths in the piping, the surplus length of any standard section can easily be cut ofi from the end of the section at which the two pipes are flush with each other. This end is illustrated the lower end in Fig. 2, but my pipe sections can equally well be used in inverted positions. v

Thusarranged, my sectional units permit an easy, inexpensive and rigid installing of an inner air pipe extending through almost the entire length of a stove pipe and for eonnecti-ng the outlet 13 of this air pipe to an upper room, as indicated for example in Fig. 1. In practice the air piping is desirably sealed at its exterior to the stove piping (as by a suitable cement) at both the air inlet and the air outlet elbows. With the air pipe freely spaced from the. bore of the stove pipe at all points except the fastenings (which can be quite small in total diameters compared with the total length of the piping), I afford a ready circulating of the hot gases all around the air pipe and hence secure the effective use of a large share of the heat of these gases.

However, while I have heretofore described the air pipe in each of my unit sections as welded to indentations in the stove pipe of the same section, I do not wish to belimited to any particular means for spacing the two pipes in each section or for securing them to each other. Nor do I wish to be limited to other details of the construction and arrangement above disclosed, since changes may obviously be made without departing either from the spirit of my invention or from the appended claims.

For example, Fig. 4 shows a transverse section through an air-circulating stove piping also embodying my invention, in which the stove pipe 3 has an inward indentation 15 abutting against and welded to an outwardly directed boss 16 formed on the air pipe 6.

Likewise, Fig. 6 shows a section through another unit, in which the air pipe 6 is spaced from the stove-pipe 3 by a spacer sleeve 17, and in which a rivet 18 extends through the spacer sleeve and the adjacent portions of both pipes to secure the pipes to each 1n thls rigidly spaced relation.

In practice, I preferably dispose the riser sections leading upward from the stove so that the air pipe is nearest to the outward stove-pipe wall, thereby making it easier for any soot in the stove pipe to drop back into the stove; and for the same reason, preferably dispose the air pipe in elbows (hke the elbow 8 in Fig. 1.) nearer to the upper than the lower side of the horizontal arm of the elbow. However, I do not wish tobe limited in these respects. If the piping needs to be cleaned after a seasons use, the sections can readily be pulled apart in the same manner as those of ordinary stove pipe, and by having the two pipes flush with each other at the lower end of each section, I permit the section to be slammed downward against any hard surface to dislodge any accumulated soot and dirt. This flush disposition of the pipes at the lower end of each setcion also permits the dealer to store these sections upright without damaging the projecting air pipe 1 portions.

spirit of my invention or fromthe appended claims.

. Nor do I wish to be hunted to the use of my air-c rculatmg twin pipe sections n connection with" stoves, for supplying hot; air to f rooms other thanthose in which the stove is disposed. For example, Fig. 7 shows sections. of my twin piping employed in connection with one of the hot air pipes leading from a furnace 18 through-a wall 1 9 of an upper room in a hot air heating system. In this case, the inner piping 21 is continued at its upper end-by a pipe 22 also leading into the same room, while the lower endof the inner piping is continued by piping 23 leading into the lower portion of the furnace- Thus arranged, the hot air rising in the pipe sections 3 to the room also prewarms air which is drawn downward (by i the draft of the furnace) as part of the air' supply for the furnace,

thereby creating a circulation which continually draws air out of the given room and prewarms it. In view of such other uses for my piping, it is'to be understood that I am using the term air circulating twin heater pipe in a broad sense in which it is not limited as to the types of heaters with which-it is employed.

I claim as my invention:

1. An air-circulating heater pipe composed of slidably interfitted sections; including main sections each consisting of a length of stove pipe and a length of smaller diametered air pipe rigidly supported within and freely spaced from the stove-pipe, the air-pipe having its axis parallel to but laterally spaced from the axis of the stove pipe; the air pipe projecting at one end beyond the stove pipe and having its other end flush with the corresponding end of the stove pipe.

2. Air-circulating heater piping composed of slidably interfitted sections; including main sections each consisting of a length of stove pipe and a length of air-pipe rigidly supported within the stove-pipe, the air-pipe having its axis parallel to but laterally spaced from the axis of the stove. pipe; and also including air pipe elbows connected to opposite ends of the sectional air pipe, each elbow extending laterally through and being exteriorly sealed to the stove piping.

3. A sectionalunit for an air-circulating l heater pipe composed of consecutively interfitted sections, comprising: an outer'pipe having one end thereof formed for telescopically interfitting the opposite end of a counterpart section, an air pipe of smaller diameter than the said outer pipe and disposed within the outer pipe eccentric of the latter and with the axes of both pipes parallel, plural securing means spaced longitudinally of the air pipe for securing the latter to the stove pipe, and

means associated with each of the securing means for spacing-the air pipe inwardly from the bore of the stove pipe.

LA sectional unit for an air-circulating heater'ipipe composed of consecutively interfitted sections, comprising: an outer pipe having one end thereof formed for telescopically interfitting the opposite end of a counterpart section, an air pipe of smaller diameter than the outer pipe and disposed within the stove pipe eccentric of the latter and with the axes of both pipes parallel; one ofthe pipes'having plural formations spaced longitudinally of that pipe and directed toward the other pipe and engaging the latter pipe for spacing the alr-plpe lnwardly from thebore of the said outer pipe; the inner pipe having one-end thereof flush with the corresponding end of the outer pipe, the other end of the inner pipe projecting beyond the adjacent end of the outer pipe.

Signed at Chicago, Illinois, December 26th, 1929. t

ROBERT ELLSDOR-F. 

